Brake Rotor Runout

[hawretre]

I noticed that my right rear wheel was getting hot. I initially thought that the emergency brake might not be completely releasing. But after lifting the car and rotating the wheel I discovered the the brake was dragging on one particular area of the rotor.

I pulled the wheel and brakes and measured the runout on the rotor at 0.0055". I then pulled the rotor, rotated it as close to 180 degrees as I could and remeasured the runout - still 0.0055". However the point of highest runout stayed at the same spot on the pin drive and not the rotor. Then measured the runout on the pin drive - 0.0021". I didn't do the math but that seems to be consistent with what I'm seeing on the rotor.

I have not pulled the pin drive as of yet. Has anyone seen a similar issue? It appears to be the pin drive or axle.

This BDR #1799 with the newer pen drives - single bolt attachment. Any idea of the torque spec on the pin drive bolt?

[FWB]

if the runout numbers you posted are correct, then i don't see a problem with 2 thou or 5 thou, your head hairs are 3 thou, i don't think your seeing 5 thou with your eye.
now if you botched the decimal point and its 50 thou then there's an issue

[Gaz64]

.005 (which is about .125mm, 1/8 mm) at the 3/4 of the braking surface is too much for my liking.

Indexing the rotor for minimum runout and no change, shows the hub face to be bent.

I like to target .001 - .002 max.

You could have the rotors skimmed with an "on car" disc machine.

Put a paint marker on one stud and corresponding point on the rotor if they need to be removed and refitted.

[spdbrake]

Gaz is right. Try indexing the rotor 1st.

If you want to correct the run-out at the hub there are a few companies that make shims. Raybestos, NAPA, and others.

https://www.youtube.com/watch?v=SSxCNbjKi-0

https://www.youtube.com/watch?v=I5Mj_G5LIz8

[hawretre]

Hey! Thanks for the quick feedback.

I have indexed the rotor. It appears that a 0.006" rotor shim is the easiest fix.

[Gaz64]

Originally Posted by hawretre

Hey! Thanks for the quick feedback.

I have indexed the rotor. It appears that a 0.006" rotor shim is the easiest fix.

How are you going to do this with shims?

Remember you said .0021 at the pin drive face?

.002 at the highest runout point, then .001 at 90 degrees either side?

So .002 at 6 o'clock, .001 at 3 and 9 o'clock, and zero at 12?

[hawretre]

Should have the shim today.

I'm guessing the difference in shim thickness will be 0.002". Maybe 0.004 at 6, 0.003 at 3 and 9, and 0.002 at 12 or something proportional.

I'll mic it before installation out of curiosity.